1. Field of the Invention
The present invention relates to a combined bead portion and rim arrangement tire and a
2. Description of Related Art
FIG. 3 shows a conventional radial tire in which a bead 52 on one side of a tire T is in engagement with a rim R on the same side. Another bead portion and another rim on the other side which are not shown in the drawing are arranged symmetrically with the illustrated side. The rim R has a bead seat 50 extending in a direction going away from the rim cross sectional center plane RC, and a flange 51 standing at the distal part of the bead seat 50 and being curved outwardly. The bead 52 is formed adjacent to and on a line extended from a sidewall portion 53 of the tire T. In FIG. 3, the numeral 54 represents bead wires, the numeral 55 represents an apex which is a layer of hard rubber or the like, and the numeral 56 represents a bead filler which is a layer of reinforcing cords or the like.
In such a conventional tire bead to rim structure, the bead 52 of the tire T is engaged on the bead seat 50 of the rim R and supported in a sideward direction by the flange 51, and brought into close contact with the bead seat by internal pressure P in the tire T, and this enables the seat to maintain internal pressure P so that the required function of the tire T can be successfully exhibited. For this purpose, the tire T has the apex 55 made of, for example, hard rubber and disposed usually at a location radially outside of the bead wires 54 in order to maintain the tire sectional shape to provide the lateral rigidity, and additionally the tire construction usually comprises the bead filler 56 enclosing the apex 55.
However, the above mentioned conventional construction has drawbacks explained below. Firstly, the bead portion 52 needs to have a substantial volume to ensure lateral rigidity, and accordingly the components such as the apex 55, the bead filler 56 and the like need to be large, Secondly, the whole internal pressure P of the tire T is acted on by the bead wires 54 through the tire casing, and accordingly the bead wires 54 need to have high strength. These requirements require substantial tire weight and a number of production steps, and leads to the problem of a uniform vulcanization or cure of the tire, becoming difficult to achieve.
A modified type of tire-rim engagement has been proposed wherein the bead portions of the tire in cross section additionally have a laterally-outwardly-formed ridge made of solid hard rubber. The bead seat of the rim on this tire has in cross section a distal part which defines a concave space to accomodate the ridge in such a manner that all the radially inward surface of the bead portion and the radially inward, the laterally outward, and radially outward surfaces of the ridge are brought into close contact with, the bead seat of the rim. The bead seat may also have a rib at a laterally inner location to prevent the engaged bead of the tire from moving laterally inward to become out of engagement with its seating.
However this modified type of tire-rim engagement has the following drawbacks. Firstly, the weight of the bead portion is increased because of the additional solid hard rubber ridge. Secondly, a tight dimensional tolerance of the bead portion is required because the bead portion is designed to be in contact with the bead seat in three directions, i.e. radially inwards, laterally outwards and radially outwards, and simultaneously with the rib on the bead seat, when the bead portion is brought into engagement with the rim. Thirdly, the assembly work of the tire and the rim requires extra time and labour to engage the solid hard rubber ridge.
Further, with respect to fixation of a bead of a tire to a rim, there have been proposed various kinds of fixation as can been seen in, for example, British patent No. 22300 by Griffith, British patent No. 5971 by Veith, U.S. Pat. No. 480,595 and German patent No. 190039. These patents disclose tire and rim assemblies wherein beads extend laterally outwards of the tire and rims have portions extending laterally inward direction.
However, in the above tire and rim assemblies, the fixation of the tire to rim is carried out by mechanical engagement (i.e. such fixation that is performed by engagement between a projection and a concaved portion or a recess). Accordingly, in such an arrangement, assembly of a tire and a rim cannot be carried out if the rim is not separable or if the tire is not made of very soft material. When the rim is separable, the fixation of the tire to the rim becomes weak or unstable, and the operation of assembly becomes time-consuming.
An object of the invention is to solve the problems mentioned above and to provide a tire and a rim having a construction that is not only simple, but also small in volume and light in weight. Also, the number of bead wires is reduced, no additional degrees of tolerance are required, the assembly can maintain a safe running capability even in an air-loss condition, and the tire is easy to assemble with the rim.